The present invention relates to a handrail for use with escalators, travelators and similar, which has a C-shaped cross-section, a sliding layer and a rubber covering layer for the user as external layers, also a layer exhibiting a tension carrier, more especially steel cords embedded in the rubber and oriented in the longitudinal direction, and at least one strengthening layer on each side of the tension carrier.
Handrails for escalators, passenger-conveying travelators and similar have to fulfil important functions. They must provide a stable and secure grip for people using the escalators and travelators and must be of a flexible design such that they can bend and be carried around the various driving rollers. Handrails must also be capable of withstanding stresses of several thousand Newton.
A handrail design of the type specified initially is known for example from U.S. Pat. No. 5,255,772. The type of handrail with C-shaped cross section disclosed there exhibits a tension carrier which consists of steel cords running parallel to each other in the longitudinal direction of the handrail, which are embedded in a rubber matrix. The sliding layer consists of a closely woven material, for example, cotton, polyamide or polyester, and must ensure that the handrail slides well on the guide rails. On each side of the tension carrier there are provided strengthening layers consisting of a woven material whose warp threads are oriented in the transverse direction of the handrail, thus at right angles to the tension carrier. The various weft threads provided merely serve to hold the warp threads together.
The necessary rigidity is supported by the C-shaped cross-section of the handrail. The lip width is specified so that the handrail can slide without the resistance being too high but the lip width tolerance must be sufficiently small that pinching of fingers or clothing cannot occur. Generally, handrails of known designs either tend to enlarge the lip distance, which can lead to pinching of fingers or clothing, or they tend to become narrower. In the latter case this can result in friction between the handrail and the rails, overheating and subsequently destruction of the handrail.
The problem for the invention is thus to develop a handrail for escalators and passenger-conveying travelators, having improved dynamic properties and improved dimensional stability and a longer life compared with known designs, which does not exhibit the afore-mentioned problems.
The problem set out is solved according to the invention by at least one of the strengthening layers being a rubber layer with uniformly distributed short fibres which exhibit a preferential orientation and run at an angle other than 0xc2x0 to the longitudinal direction of the handrail.
The present invention provides a handrail having higher transverse rigidity, higher longitudinal flexibility, improved dimensional stability and more rigid lips compared with known designs. The material provided uniformly with short fibres used for the strengthening layers according to the invention impedes the appearance of various stresses which occur in conventional handrails during application of stress in the area of transitions from textile to rubber.
Moreover, the strengthening layers in the handrail are positioned such that the short fibres run at an angle other than 0xc2x0 to the extension of the tension carrier. A strengthening layer according to the invention also contains no warp fibres which are present in conventionally constructed handrails in the strengthening layers of woven material. The absence of warp fibres gives the handrail constructed according to the invention an excellent elasticity in the longitudinal direction with higher transverse rigidity at the same time. In addition, for the handrails according to the invention the change in the lip width both under positive bending and also under bending via the handrail back (negative bending) is substantially smaller than for conventionally constructed handrails. Handrails constructed according to the invention are easy to manufacture, have a considerably longer life than known designs and are generally safer to operate than known designs.
According to a preferred embodiment of the invention, the short fibres in the strengthening layers are oriented such that they run at an angle to the longitudinal direction of the handrail, which differs from the longitudinal direction of the handrail by at least 30xc2x0, and more especially by at least 45xc2x0. An orientation of the short fibres in these regions is an advantage for the elasticity in the longitudinal direction and also for high transverse rigidity.
A handrail according to the invention can be executed differentially depending on requirements and intended usage. In particular, on one or on both sides of the tension carrier layer there can be provided at least one each, more especially two strengthening layer(s) each, provided with short fibres.
The rigidity of the handrail according to the invention is favourably influenced if the short fibres in the neighbouring strengthening layers cross and form preferably the same angles with the longitudinal direction of the handrail. An alternative to this can be a design where the short fibres in neighbouring strengthening layers run parallel to each other.
In order to achieve the desired transverse rigidity, longitudinal flexibility and dimensional stability it is favourable if the fraction of short fibres is between 10 and 40 parts by weight, more especially between 15 and 30 parts by weight, relative to 100 parts by weight of rubber in the mixture.
As regards the material for the short fibres, this can be a synthetic material such as nylon, polyester, polyvinyl alcohol, aromatic polyamide, carbon, a mineral material such as glass or a natural material such as cotton. The short fibres used can also be a fibre mixture comprising fibres of different materials. The rigidity of the strengthening layers can thus be co-determined by the choice of fibre type and the mixture ratio of possible different fibres.
The ratio of the fibre length to the fibre diameter is also a co-determining factor for the rigidity of the layers. This ratio should be between 50 and 300 for the fibres used.
Depending on the intended usage and other requirements and also depending on the fibre material, fibre fraction etc, the strengthening layers in the finished handrail ultimately have a thickness between 0.8 and 5 mm.